Carl M. Conrad

Kinetics of the Pyrolysis of Cotton Cellulose

The kinetics of decomposition of cellulose were studied in the temperature range of 270°-310°C with absorbent cotton and ball-milled scoured cotton, both cut in a Wiley3 mill. The decomposition of cellulose was carried out in a thermogravimetric analysis (TGA) apparatus having precise temperature control, under continuous now of helium gas. The study of the kineties was followed by the determination of the residual weight up to the limiting end point. The data furnished evidence of a complex reaction behavior up to about 40% decomposition and a first-order reaction thereafter. The major reaction of the decomposition of the cellulose molecule was considered as a two- step process: glucosidic bond scission and subsequent levoglucosan formation. The kinetics of a chain reaction mechanism have been proposed and shown to be con sistent with the experimental data. The energy of activation for the initiation reaction of the original cotton and the hall-milled cellulose was found to be 54.3 kcal/mole and 75.0 kcal mole, respectively. These large differences are believed to be due to differ ences of the fiber structure, induced in the latter case by ball mining. For the propa gation reaction, the activation energy values were 33.0 kcal mole and 37.1 kcal/mole, respectively.

Thermal Degradation in Tire Cords Part I: Effects on Strength, Elongation, and Degree of Polymerization

of any mechanical action. No attempt is made to answer the question concerning any possible mechanical degradation, such as has been observed under certain conditions by others [7, 10, 12], inasmuch as such mechanical degradation in road operation is inextricably bound up with the heat produced at the same time. The present investigation was designed to amplify and, if possible, explain the earlier work of Conrad, Lyons, and Tripp [3] which showed that cotton tire cords taken from tires that

Improvements in the Acid-Hydrolysis Method of Determining the Crystallinity of Cellulose

In a study of the acid-hydrolysis method [5] for the determination of the degree of crystal linity of cellulose fibers, a technique has been developed for the solvent removal from the hydrolysis residues of all but traces of the humic substances which are formed from the soluble hydrolysis products and which interfere with the crystallinity determination. Although ammonium hydroxide and pyridine were effective solvents, hot 50-percent aqueous monoethanolamine was found to be the most practicable means of removing these humic sub stances. Its effectiveness was demonstrated (a) by showing that the weights of the extracted residues were the same as the weights of residues corrected by computations based on data from experiments with glucose; (b) by varying the liquid-solid ratio during hydrolysis and showing the uniformity of the weights of the resulting ethanolamine-extracted residues; and (c) by obtaining equal extrapolated values for degree of crystallinity from parallel extracted and un extracted but mathematically corrected hydrolysis series. Data are presented to show that preliminary extraction with either 1-percent sodium hydroxide or ethanolamine to remove the noncellulosic constituents does not change the crys tallinity values of samples of cotton and cotton linters. A revised crystallinity procedure is described which incorporates the improvements de scribed above.

Convenient Adjustment to a Standard Velocity Gradient of the Fluidity of Anomalous Cuprammonium Solutions of Cellulose

Although structural viscosity has been recognized for many years and has been intensively studied since about 1930, a satisfactory theoretical and experimental basis for dealing with the viscosity of linear high polymer solutions has not been found Of the great mass of data on the subject published in the literature, few can serve a permanent purpose because not all the conditions necessary for interpretation have been recorded. Yet by continued attack and by study of such findings as those of Peterlin

Some Possibilities and Limitations of X-Ray Methods for Measuring the Strength of Raw Cotton

TT~URING recent n~onths f)’e<(nent <)ues1io))s have come fotl)e(B)tton DlTHING C’t’(’111 1II01llh 1’1’1’</&dquo;(’111 qlll’H1iollH 11:1B’1’ (’1111)(’ i 1hl’ (iO/ OIl jj ’)’(’(’1J1lo1og’j(’;¡1 Lahol’:l1ol’Y J’I’g:ll’clillg 11,1’ ,.I:I&dquo;,....ifj,’:l1ioll of mnitou by X-ray methods. Amury tlm (I1H’s1ioIlS !I:IB’(’ bl’l’1I :-;twh :1&dquo;4 Can the X-ray method be used to classify cotton? Have you fomnl the 1-ray method satisfactory? How accurately does the ~’-r;ry method j>I<,,li<.< the spinning B’11111(’ of the cotton? How mud) does the «<jiiij>mi<>if <.1>,1 .> Ifrm~

Effect of Grinding on the Crystallinity of Cellulose Fibers, as Indicated by the Acid-Hydrolysis and Other Techniques

A study was made of an effect previously noted, that grinding cotton fibers in a Wiley mill causes a reduction in degree of crystallinity as determined by the acid-hydrolysis method. It is shown on samples of purified linters and cut cotton, ground under conditions of increasing severity, that even mild grinding—for example, through a 2-mm. sieve—causes a detectable reduction in indicated degree of crystallinity, and that as the severity of grinding increases the degree of crystallinity drops correspondingly. This drop is not caused by passage of more of the finely ground particles from the more severely ground samples through the filters. When the ground samples were moistened with water and allowed to dry, a portion of the lost crystal linity was regained. The acid-hydrolysis results are supported by accessibility, heat of wetting, and moisture adsorption measurements, which, with few exceptions, indicate increasingly larger amounts of amorphous material in the samples receiving the more severe grinding. While the x-ray diffraction patterns did not reveal any effect of the most severe grinding, it is assumed that the changes were not sufficient to permit their detection by this means. Some implications of the results on the interpretation of cellulose structure are discussed.

The Transformation of Acetylated Cotton Cellulose From Triacetate I to Triacetate II with Retention of the Fibrous Form

. Sprague and co-w orkers [ ? ) studied the etfect of various organic media on the crystal structure of cellulose triacetates I. and I I. They state that if the triacetate I. foriiie(I hy heterogeneous acetylation of the cellulose with retention of fibrous form, is dissolved in an organic solvent and then precipitated out. the product is always in the triacetate II form. However, they were unahle to obtain transformation of the triacetate ! I to triacetate lI I hv swelling. without loss of nbrous form. They also concluded that upon saponincation. triacetate I is always converted to the native or cellulose I furiii. while triacetate II is always converted to the cellulose II form.

X-Ray Diffractometer Thermal Technique for Study of Structural Changes in Cellulosic Compounds1

Previous x-ray diffraction studies of cellulose derivatives and other organic com pounds have shown that heat often has important effects, facilitating crystallization, transitions, and polymorphic transformations. However, the application of heat treat ments in conjunction with x-ray diffraction studies has usually been laborious, inexact, and at times ambiguous because of limitations of the technique. The present paper describes the adaptation of an x-ray furnace in conjunction with a two-pen potentiometer recorder and temperature-program controller to overcome some of the previous limita tions. A specially designed specimen holder is described. Thermal diffractograms of cellulose acetate and of benzyl and cyanoethyl cellulose are reproduced to demonstrate some of the advantages and possibilities of this technique.

Viscometric Studies of Cellulose in Cotton in Relation to Mechanical Processing

A study was undertaken at the Southern Regional Research Laboratory to determine whether or not the mechanical processing of cotton fibers into yarn causes any chemical degradation to the cellulose. The study seemed timely in view of a report [22] indicating that the mechanical processing of cotton into yarn by conventional textile machinery causes as much as 30% average reduction in intrinsic viscosity. Studies were made on four sets of samples which had been treated as follows: (1) powdered in a Wiley mill; (2) processed a number of times through a new type of textile cotton opener developed at the Southern Regional Research Laboratory; (3) mechanically processed in essen tially the same manner as in the study referred to above; and (4) portions of the same samples used by Krieble and Whitwell [22]. The viscosity measurements determined by the methods employed at the Southern Regional Research Laboratory failed to show any demonstrable chemical damage to the cellulose which could be associated with processing. When the new method described by Krieble and Whitwell was applied to the viscosity data, the linear plots depended upon for extrapolation could not be obtained. It was concluded that the damage previously reported to have been found is not fully supported by a statistical treatment of the data; also, that chemical damage is not produced in ordinary cotton textile processing to any appreciable extent, although it might conceivably become notice able in excessively processed cotton. Some suggestions are given to explain the failure to secure linear plots by the suggested new method.

Pectic Substance of Cotton Fibres in Relation to Growth

The content of pectic substance in cotton fibres at various stages of growth was determined. The results suggest three distinct stages of de velopment of the fibre. The first extends to about the 18th day and is char acterized by a gradual decrease in the content of pectic substance. The second extends from the 18th to about the 35th day during which time there occurs a rapid decrease in the content of pectic substance. In the final stage, which extends from about the 35th day to maturity, there is only a slight decrease in the content of pectic substance. These three stages of de velopment are in good agreement with those deduced by other investigators from different types of data.